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rear derailleur chain rubbing in only one gear

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rear derailleur chain rubbing in only one gear

Old 04-20-13, 08:07 PM
  #1  
Bahnzo
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rear derailleur chain rubbing in only one gear

This is (somewhat) driving me crazy. Just like the title states, my chain rubs and makes a clicking noise from the rear derailleur, but only in one gear.

Details: 1986 schwinn, so friction shifting, 3 chainrings, 5 speed freewheel. In middle chainring (And top ring, have to admit now that I'm not sure if it happens in the low ring) the 23 tooth gear causes a rubbing/clicking on the chain. This only happens in this gear and every other is silent and fine.

The only hint I have is that the "hang" of the derailleur increases/lessens the amount of rub. IE: if I move the angle up/down it changes/increases the amount of rub.

So. First, what other information could I provide to solve this? I'm pretty new, so please forgive me for not using correct lingo or providing enough/correct info (I'm a tech support guy, so I know the frustration in that).

Second: HELP! It's maddening that I can't figure this out. I can't understand if something's bent (seems if that's the case, then why happen in only one gear?) or what?

Thanks!
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Old 04-20-13, 09:14 PM
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Question. Does the derailleur have a so-called B-screw on top whereby you can adjust the hang angle?

If so you've answered your own question. Use the B-screw to lower the derailleur so you have proper clearance in all gears.
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Old 04-20-13, 09:27 PM
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Originally Posted by FBinNY View Post
Question. Does the derailleur have a so-called B-screw on top whereby you can adjust the hang angle?
Thanks, but no, there is no B-screw. I looked for that right off, but the derailleur I have does not have one.
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Old 04-20-13, 09:45 PM
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You didn't say, but I'll assume this is a derailleur where the cage pivot is between the pulleys. On these the upper pulley moves up and down with changes in chain take up. Sometimes you can work the chain length to pull the cage around and improve clearance. Otherwise, you might improvise a way to lower the RD, by using some fill behind the stop on the hanger. I've done this using "plastic metal" epoxy filler, reinforced with a piece of scrap metal, such as a 1/8" bearing ball, or a piece cut from a spoke.
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Old 04-20-13, 09:50 PM
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Originally Posted by FBinNY View Post
You didn't say, but I'll assume this is a derailleur where the cage pivot is between the pulleys. On these the upper pulley moves up and down with changes in chain take up. Sometimes you can work the chain length to pull the cage around and improve clearance. Otherwise, you might improvise a way to lower the RD, by using some fill behind the stop on the hanger. I've done this using "plastic metal" epoxy filler, reinforced with a piece of scrap metal, such as a 1/8" bearing ball, or a piece cut from a spoke.
I'm a little unsure what you mean exactly, but here's what I have:

sachs huret eco duopar.
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Old 04-20-13, 10:01 PM
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DouPar RDs have a unique double articulation, unlike any other derailleurs. IMO they're derailleurs that only Frank Berto could like.

There's lots of commentary about these, though most is 30+ years old. Search Huret Doupar and link to some discussions which might give you some insights.
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